1. Field of the Invention
This invention relates to fluid damping control for vehicle suspensions, such as the suspensions of bicycles, which are typically mounted between the bicycle frame (chassis) of the vehicle and a wheel of the vehicle.
2. Description of the Related Art
Shock absorbers used on motorized and human powered vehicles provide a means to damp out road vibration, bump energy and substantially increase rider/passenger comfort. The shock absorber component is composed of two parts. First being the damper, the component that absorbs the bump energy and, second the supporting spring. It is common in high performance shock absorbers to have an external reservoir that shock fluid can circulate to. The fluid that circulates to the reservoir is a result of the shock shaft insertion at the shock absorber. The insertion of the shock shaft onto the shock body will occupy a volume that displaces the oil towards the reservoir. This reservoir can be mounted to the main shock absorber or connected by means of a length of high-pressure hose.
Under certain circumstances it is advantageous to restrict the flow of oil (incompressible fluid) into the reservoir. The function of flow restriction aids in creating compressive direction damping, referred to as compression damping. Compression damping will be created at the reservoir when fluid is displaced from the shock absorber. The combination of flow restriction at the main piston within the shock absorber, for example as a result of flexible washers sealing holes on the main piston, coupled with compression damping at the reservoir provides the total compression damping created by the shock absorber system. The devices used to create compression damping in the reservoir are of many types. A plate covered by flexible washers is one example of a device. Other methods employ passages blocked by movable balls or plates forced into position by a spring. A further type of device uses a simple passage that is restricted by a movable protrusion that changes the clearance between the passage and protrusion.
Another feature known in the art for providing compression damping in an internally-pressurized shock absorber is an annular cavity containing compressible fluid formed between the main shock absorber piston and the piston rod. A second annular piston in sealed engagement with the cavity is driven by pressure forces and reciprocates in the cavity to alternately block the compression damping passageways in the main piston as the piston approaches the blind end of the shock absorber cylinder, and unblock them as the piston withdraws from the blind end. The annular cavity and the annular piston which reciprocates within it are configured coaxially on the main piston and shaft of the shock absorber. See also U.S. Pat. No. 5,190,126.
There is a need in bicycles, motorcycles, and other vehicles which incorporate fluid suspension shock absorbers for a pressure-controlled damping circuit in a separate, non-coaxial reservoir. All prior-art methods, such as those noted above, suffer from various limitations, including an impact on the travel capability within a given shock absorber length, fixed location and installation requirements, and limited adjustment range.